I think it's a very odd way of wording it. "Why?" follows naturally, but assuming you would want some particular diagnosis seems uncalled for and even intrusive. His next question should have been: " Do you think you fit that particular diagnosis?. What makes you think that?" There's a forum for training and new psychiatrists that seems to me to have a very narcissistic view of patients. They have a long thread of people coming to their office, claiming wrongly to be suffering from bipolar. (the pd's say). There wasn't a single response that explains why the psychs would think people would do that. Not one. That's what your doctor's second question reminded me of It's assuming a lot to believe a patient wants to have a particular diagnosis.